There are multiple earphone standards, mainly including two international standards: European standard earphones and American standard earphones, and the greatest difference between the two types of earphones is that the positions of the Grounding (GND) area and the Microphone (MIC) area on the two types of earphones are different from each other. All electronic devices supporting multimedia playing are required to be compatible with both European standard earphones and American standard earphones. In the current electronic devices, a microprocessor is usually adopted to recognize the type of an earphone. However, such a recognition circuit is complex in design, relatively higher in cost and poor in recognition accuracy.